Reference report: Energy self-sufficient house

The world’s first fully energy self-sufficient house has been built in Brütten, Switzerland. A DC/DC converter from ARADEX works in the basement.

The project

The house with nine residential units, located near Zurich, is the world’s first fully energy-sufficient house – without any external connection for electricity or gas as well as without an oil tank. The energy needs are met mostly by solar energy. Empirical values are now available that prove the success of the project.

The key facts

  • No external power supply – either from oil, gas, or electricity
  • The energy demand is met 100 % from regenerative energies
  • The primary energy source is the sun
  • Short-term and long-term storage allows the entire energy demand to be met independently of the time of year
  • The generated solar electricity is stored in the form of hydrogen
  • The long-term storage system uses fuel cell technology
  • The generated electricity is used to drive an electric car as well as to supply energy to the house

The challenge

The central challenge for the focus on solar energy was the location of the house. During the winter in Switzerland, there is a lot less sun than in the summer, but more energy is required for heating purposes. At the same time, the energy supply for the entire building has to be ensured during the dark, heating-intensive time of the year as well.

The implementation

Most of the energy is generated via the photovoltaic cells mounted on the roof and on the façade. The energy generation therefore depends on the duration and intensity of the solar radiation. To guarantee the energy supply throughout the year despite the very strong seasonal fluctuations in the amount generated, a revolutionary network of different storage systems was designed. The en-ergy that is “lacking” during the winter months is generated in the summer, thereby compensating for the deficit in the winter. This requires efficient storage technologies.

Short-term storage

Short-term storage: In addition to the photovoltaic system, the building has a heat pump. The heat pump is driven by the photovoltaic current as well but also uses other heat sources such as the outside air, two geothermal probes, and the waste heat from the hydrogen production. The energy generated by the heat pump is stored in batteries and routed into the apartments through floor and wall heating systems.

Long-term storage

In the basement of the house, the electricity generated via the PV system is converted into hydrogen with an electrolyzer and then stored in tanks. On days with little sun, fuel cells are used to convert the hydrogen into electrical energy (power to gas) in order to meet the energy needs of the house. This is where the DC/DC converter from ARADEX (type VP5000-DCDC200-HL) supports the fuel cell from Proton Motors Fuel Cell. Since the voltage level of fuel cells is subject to considerable fluctuations, it must be increased for optimum integration of the fuel cell in the energy supply system. This is ensured by the DC/DC converter. In this system, the DC/DC converter increases the output voltage of the fuel cell from 50-100 VDC to the system voltage of 700 VDC.


In addition to the connection of the fuel cell, the DC/DC converter also balances the voltage level of the battery used in the short-term storage system, allowing efficient use of the battery and the fuel cell.

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